The invention relates to mineral fibre producing techniques in which the material to be fibered is carried in the molten state over the periphery of centrifuging wheels, is conveyed by these wheels and then becomes detached therefrom in the form of fibers under the effect of centrifugal force. In these techniques, more often than not a plurality of wheels are used which are disposed in proximity to one another. The material poured onto the first wheel is accelerated and thrown onto the following a wheel. A part of this material forms fibers and the excess is passed on to the following wheel to result in formation of additional fibers.
These fiber producing techniques are very currently used industrially with materials for which the processing temperature is relatively high. In particular, they are materials such as basaltic rocks, blast furnace slag or compositions based on such slag, and more generally all glasses which only melt at an elevated temperature.
Employing these techniques is interesting from various points of view. For example, fibers produced by using glasses having a high melting point are advantageously used in materials which have to be fireresistant. The cost of producing these fibers is therefore relatively moderate in relation to that for other fiber forming techniques. However, this type of technique does have certain drawbacks. One of the most important is the fact that even when choosing the best conditions known to date, the efficiency of the operation is not entirely satisfactory. With the fibers, a not inconsiderable quantity of unfibered products is formed which reduces the efficiency of production. Furthermore, despite systematic elimination, part of the unfibered products remains in the products obtained, the properties of which become modified.
For these reasons, improvements in these techniques resulting in better conversion of the molten mass into fibers are desirable and many attempts have been made along these lines.
Some investigators have been mainly concerned with the conditions of centrifugal processing and have sought better combinations of diameters and speeds of wheel rotation. Others have devoted their attention to the wheel environment and in particular to the gas currents blowing along the wheels and intended to separate the fibers from the unfibered matter or even to the drawing of the fibers.
Many proposals have been forthcoming which likewise relate to the surface condition of the wheels to encourage "hooking on" of the material and therefore drawing of the fibers.
Substantial improvements have been obtained. Nevertheless, increased efficiency is still desirable.